1. Field of the Invention
This invention relates to a developer carrying member and a developing assembly.
2. Description of the Related Art
In one-component developing methods employed in electrophotography, developers do not contain any carrier, and hence it is unnecessary to change a carrier for new one with deterioration of the carrier. It is also unnecessary to provide developing assemblies with any mechanism for controlling the concentrations of a toner and the carrier, and hence developing assemblies themselves can be made small-size and light-weight.
Now, under needs in recent years for making image quality much higher, Japanese Patent Application Laid-Open No. 2001-312136 discloses a developer carrying member containing in a resin layer as a surface layer a copolymer which contains a quaternary ammonium base as a charge control agent and also a developing assembly which makes use of such a developer carrying member so as to provide the toner with triboelectricity in a higher quantity. The developer carrying member according to Japanese Patent Application Laid-Open No. 2001-312136 can make the resin layer low in its volume resistance because negative-polarity counter ions of the quaternary ammonium base in the resin layer are ionized to make the resin layer have ionic conductivity. As a result of such a low volume resistance, the developer carrying member can prevent ghost and fog from occurring in electrophotographic images, as so considered.
As a result of further studies made by the present inventors on the invention according to Japanese Patent Application Laid-Open No. 2001-312136, they have discovered that any density decrease, density non-uniformity and spots of toner around images may come about in electro-photographic images when the developer carrying member according to Japanese Patent Application Laid-Open No. 2001-312136 is used in a one-component developing system.
Accordingly, the present invention is directed to providing a developer carrying member, and a developing assembly, which can stably provide the toner with triboelectric charges, may less cause any problems such as image density decrease, density non-uniformity and spots around images even during running on a large number of sheets, and can enjoy a stable and good developing performance.